There is a significant interest in the development of photonically implemented antennas for military and commercial communication and RADAR applications. Several candidate architectures under investigation are active phased arrays, direct radiating multiple beam antennas (MBA), and array-fed-reflector MBAs. Most demonstrations and experimental investigations to date have been constructed with relatively few elements and passive optical systems to and from the array elements. In the future, practical antenna systems achieving useful levels of performance will require active distribution of optical power to as many as hundreds or thousands of individual array elements.
Active optical distribution components, realized using the self-imaging properties of multi-mode interference (MMI) cavities, represent an integrated enabling technology for these types of systems. An active MMI based optical splitter also represents a potentially compact and reliable, electrically pumped unit for active distribution nodes in increasingly more prolific ground based digital or analog, single or multiple wavelength fiber-optic networks.
An example of such a splitting device is described in the related application by Zmudzinski. The related application discloses and claims an active multimode optical signal splitter with an optical multimode waveguide which allows for signal splitting and current pumping in order to provide optical power amplification and minimize losses due to signal splitting. The type of device described in the related application falls into the broader class of optical signal components known as the simultaneous optical splitter/amplifier or SOSA.
The SOSA has been established as a useful and potentially critical component in several optical systems such as phased array radar and optical signal processing. In essence, the SOSA is a MMI splitter, which has the added feature of optical gain. As the optical signal is split (attenuating the signal), the pumped semiconductor material provides gain to the light (amplifying the signal). The output of the SOSA consists of multiple outputs, each of which can have the same intensity as the original inputs.
While the SOSA may prove to be an integral component of optical signal distribution systems, it would be more useful if it could operate over an extended wavelength range or optical bandwidth, enabling its use in wavelength division multiplexing (WDM) systems. In conventional SOSAs, the optical bandwidth is a function of the splitter wavelength response and amplifier optical gain response, which are aligned in order to maximize performance for a single wavelength. This conventional configuration of a SOSA, however, limits their application to multi-wavelength signal distribution systems.
As such, an optical signal splitter/amplifier whose bandwidth is greater than the bandwidth of the individual splitter and gain components would provide numerous advantages.